1. Field of the Invention
The invention relates to electron processing, and in particular to the sterilization of containers by energetic electrons.
2. Description of the Related Art
The application of energetic electrons to the sterilization of food/pharmaceutical containers has attracted considerable effort in the past(1), much of which has focused on treatment of the food contact surfaces in form-fill-seal(2) or the treatment of preformed containers tumble packed and bagged(3). Techniques have been published(4, 5) on the in-line electron treatment of containers, typically blown polymers, for application to high speed filling lines. One of the major problems facing the adaptation of such a process to pre-sterilized (aseptic or esl, extended shelf life) filling machinery is the requirement of providing a completely sterile container to the filling equipment. Two major problems exist in this application:                1. The need to support the container in order to control its transport through the sterilizer and        2. The need to control its position and vertical orientation into the filling machine, usually of rotary design.        
If inadequate electron energies are used for full penetration of the container walls as in the low energy processes taught earlier(2), then special precautions are necessary in the filler in order to prevent any contamination of the contents by microorganism convective transport to the fill spout/container mouth area or transfer contamination of the pre-sterilized filler region itself by surface borne microorganisms.
Pneumatic transport techniques have been developed(6) and are widely used on such equipment by which the container is moved along horizontally on rails located in grooves blown or molded into the container for this purpose, usually under the container's neck. The fact that these rails must remain in contact with bottles moving at up to 1 m.sec−1 in a high speed filler, means that no time is available for bottle rotation or exposure of the rail contact areas and, of course, these sections exposed to the electron beam must be water cooled for dissipation of the electron energy absorbed in the rails.
If a more traditional conveyor is employed, using vacuum hold-down of the erect bottles, for example, then the interface between the bottle bottom and the conveyor plate is inaccessible to the sterilizing flux of energetic electrons. Hence its transport from the in-line sterilizer to the filler can lead to fill-zone contamination. Techniques are available for HEPA or sterile air isolation of the fill-spout/container neck area, but the possibility still exists for the transport of viable microorganisms remaining on the container bottom to the critical, pre-sterilized regions of the filler.
This application teaches techniques, verified experimentally with electron dosimetry, which permit complete sterilization of blow-molded bottles and other open-mouthed containers. It employs container presentation techniques which allow electron access to all surfaces of the container and which do not require rigid gripping or the use of devices which block electron access to those contacted surface areas of the container during the sterilization process.
Current practice for bottle sterilization/disinfection utilizes liquid disinfectants such as paracetic acid and/or hydrogen peroxide, or they may be applied in a spray form. For liquid treatment this requires an extended holding time (8–10 s) of the solution in the container in order to be efficacious, followed by washing and drying to remove residual contaminants on the food contact surfaces. This sequence required large accumulation areas at the filling speeds of interest (e.g. 10 sec−1 at 16 oz) and special environmental considerations for handling of the wastewater. Present systems utilize large star wheels, typically with neck grippers, for transport of the containers in a vertical orientation through the above steps and into the pre-sterilized filler region of the system.